patch 7.4.1658
Problem:    A plugin does not know when VimEnter autocommands were already
            triggered.
Solution:   Add the v:vim_did_enter variable.
diff --git a/src/vim.h b/src/vim.h
index a7443e9..a2dc079 100644
--- a/src/vim.h
+++ b/src/vim.h
@@ -1869,7 +1869,8 @@
 #define VV_TRUE		64
 #define VV_NULL		65
 #define VV_NONE		66
-#define VV_LEN		67	/* number of v: vars */
+#define VV_VIM_DID_ENTER 67
+#define VV_LEN		68	/* number of v: vars */
 
 /* used for v_number in VAR_SPECIAL */
 #define VVAL_FALSE	0L